Communication networks sometimes employ ring configurations. For example, some networks comprise Resilient Packet Ring (RPR) configurations, as defined by the IEEE standard 802.17, entitled “Part 17: Resilient Packet Ring (RPR) Access Method & Physical Layer Specifications,” which is incorporated herein by reference. Additional details regarding RPR network configurations and standards are available at www.ieee802.org/17.
Various communication services can be provided over ring networks. For example, a virtual private local area network service (VPLS) links different local area networks (LANs) together over an Internet Protocol (IP) network. VPLS methods are described, for example, by Kompella et al., in “Virtual Private LAN Service” (IETF draft-ietf-12vpn-vpls-bgp-06.txt, December, 2005) and by Lasserre et al., in “Virtual Private LAN Services over MPLS” (IETF draft-ietf-12vpn-vpls-ldp-08.txt, November, 2005), which are incorporated herein by reference. These drafts are available from the Internet Engineering Task Force (IETF) at www.ietf.org/internet-drafts. VPLS is also sometimes referred to as E-LAN or layer-2 Virtual Private Network (VPN).
U.S. Patent Application Publication 2006/0109802, whose disclosure is incorporated herein by reference, describes a method for delivering VPLS over ring networks. A data packet transmitted over a VPLS is received at a first node in the ring network. The data packet includes an identification of the VPLS. The first node reads the identification from the data packet. Responsively to reading the identification, the first node forwards the data packet to at least one second node in the ring network that is associated with the VPLS.